Full destruction of an anticyclonic eddy in the Northern South China Sea by Tropical Storm Mulan

The destruction of an anticyclonic eddy (AE) as a Tropical Storm, Mulan, passed through the northern South China Sea in August 2022 was observed by two Sea Wing underwater gliders. By integrating glider observations and HYCOM outputs, this study investigated 3D structural destruction and dissipation of eddy kinetic energy (EKE) within an AE. The warm and low-salinity core inside the AE was devastated by Mulan-induced strong disturbances. Intense wind stress disrupted the upper anticyclonic flow around the AE by accelerating (reversing) the flow in the western (eastern) part of the AE. These severely destroyed the unique 3D structure of the AE and led to 57 % and 96 % reductions in EKE and eddy potential energy (EPE), respectively. Furthermore, EKE budget analyses demonstrated that the EPE to EKE conversion, wind stress work, and divergence of pressure work served as dominant sources of EKE before, during, and after Mulan's passage, respectively. However, the EKE dissipation was primarily driven by Mulan-induced turbulent mixing directly during its passage and strong vertical mixing associated with near-inertial waves after its passage. To our knowledge, this is the first study to elucidate the multiple dynamic processes contributing to or dissipating dramatic EKE changes in the South China Sea over the entire tropical cyclone-eddy interaction period. These findings advance our understanding of 3D structural destruction and complex oceanic energy transfer mechanisms within the AE under tropical cyclone-eddy interactions.